#include <stdio.h>

int flag = 0;

int Sum(int s, int e)
{
    int sum = 0;
    int i = s;

    for (; i <= e; i++)
    {
        sum += i;
    }

    return sum * flag;
}

int Add(int x, int y)
{
    return x + y;
}

int div(int x, int y)
{
    if (y == 0)
    {
        return -1;
    }

    int z = x / y;
    return z;
}

int main()
{
    printf("process is running\n");

    int start = 1;
    int end = 100;
    int result = Sum(start, end);
    printf("process is done, result:%d\n", result);
    
    int a = div(10, 0);
    printf("process is done, div result:%d\n", a);

    int b = Add(10, 20);
    printf("process is done, add result:%d\n", b);

    return 0;
}
